1. Field of the Invention
The present invention relates generally to radar used for tracking multiple targets. More specifically, the present invention relates to a method for solving for the angular position of two RF (radio frequency) signals.
2. Description of the Prior Art
Currently, military tracking radar is widely used to track targets and threats, such as enemy aircraft because of its high degree of accuracy and relative immunity to electronic countermeasures that can degrade tracking radar and their associated methods of tracking. Generally military tracking radar uses a single RF pulse to gather angle information, as opposed to directing multiple narrow-beam pulses in different directions and looking for a maximum return to identify the target.
When there are two targets being tracked by radar, two RF signals at different frequencies are generated. The two RF signals produce a beat pattern in power return, with beats occurring at the frequency difference between the two RF signals. This beat pattern is produced by adding the RF signals and then subtracting the RF signals.
With current angle processing techniques utilized to pull out the angle of the combined RF signal, the non-linearity of the processing technique ensures that for a difference greater than five percent between the powers of each signal, the angle as averaged over a beat period is almost entirely captured by the dominant of the two RF signals.
Currently utilized angle processing techniques use averaging to pull out the dominant signal. For those cases where two RF signals are changing in power return such that the two RF signals are alternating as to which one of the two signals is dominant, there is need for signal processing techniques to recognize when one signal's angle is appearing as opposed to the other signal's angle is appearing. This requirement necessitates that the angles for the two RF signals be sorted in time.
Further, since only one of the two RF signals is visible during any given time period, two types of adverse situations can occur with present angle processing techniques. First, the RF signal being analyzed can be dominated by the other RF signal during a critical time period, such that the RF signal information is being extrapolated. Second, the sorting of each RF signal can be confused by environmental angle disturbances.
Accordingly, angle processing would be substantially improved if both RF signals' angles are calculated simultaneously, even when one RF signal dominates the other of the two RF signals.